http - ETag 的语法？

Question

Redbot报告我的网页标题无效:

The ETag header's syntax isn't valid.

我的标题设置为:

ETag: 4ae413bd

为什么无效？

ETag 的语法是什么？

Answer 1

试试 ETag: "4ae413bd"。ETag 的值必须遵循 ABNF形式:

  entity-tag = [ weak ] opaque-tag
  weak       = "W/"
  opaque-tag = quoted-string

  quoted-string  = ( <"> *(qdtext | quoted-pair ) <"> )
  qdtext         = <any TEXT except <">>
  quoted-pair    = "\" CHAR
  CHAR           = <any US-ASCII character (octets 0 - 127)>
  TEXT           = <any OCTET except CTLs, but including LWS>
  OCTET          = <any 8-bit sequence of data>
  LWS            = [CRLF] 1*( SP | HT )
  CTL            = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
  CRLF           = CR LF
  CR             = <US-ASCII CR, carriage return (13)>
  LF             = <US-ASCII LF, linefeed (10)>
  SP             = <US-ASCII SP, space (32)>
  HT             = <US-ASCII HT, horizontal-tab (9)>

，基本上是 ([wW]/)?"([^"]|\\")*" regular 正则表达式。

请注意，"\" 和 "/" 都是 etag 的有效值。

引用文献:section-14.19 , section-3.11 , section-2.2 .